Four diclofenac complexes with cobalt(II) and nickel(II) ions: Synthesis, spectroscopic properties, thermal decompositions, crystal structures, and carbonic anhydrase activities

Article abstract of DOI:10.1080/00958972.2014.903327

Cobalt(II) and nickel(II) complexes with diclofenac (dicl) in the presence of nitrogen-donor 3-picoline (3-pic) and 1-(2-aminoethyl)pyrrolidine (2-aepyr), [Co(dicl)₂(3-pic)₂] (1), [Ni(dicl)₂(3-pic) ₂(H₂

Full text of DOI:10.1080/00958972.2014.903327

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Four diclofenac complexes with
cobalt(II) and nickel(II) ions: synthesis,
spectroscopic properties, thermal
decompositions, crystal structures, and
carbonic anhydrase activities
Sema Caglara, Ismihan E. Aydemira, Murat Cankayab, Mehmet
Kuzucub, Ersin Temelc & Orhan Buyukgungorc
a Faculty of Arts and Sciences, Department of Chemistry, Erzincan
University, Erzincan, Turkey
b Faculty of Arts and Sciences, Department of Biology, Erzincan
University, Erzincan, Turkey
c Faculty of Arts and Sciences, Department of Physics, Ondokuz
Mayis University, Samsun, Turkey
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Accepted author version posted online: 12 Mar 2014.Published
online: 04 Apr 2014.
To cite this article: Sema Caglar, Ismihan E. Aydemir, Murat Cankaya, Mehmet Kuzucu, Ersin
Temel & Orhan Buyukgungor (2014) Four diclofenac complexes with cobalt(II) and nickel(II)
ions: synthesis, spectroscopic properties, thermal decompositions, crystal structures,
and carbonic anhydrase activities, Journal of Coordination Chemistry, 67:6, 969-985, DOI:
10.1080/00958972.2014.903327
To link to this article: http://dx.doi.org/10.1080/00958972.2014.903327
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Journal of Coordination Chemistry, 2014
Vol. 67, No. 6, 969–985, http://dx.doi.org/10.1080/00958972.2014.903327
Four diclofenac complexes with cobalt(II) and nickel(II) ions:
synthesis, spectroscopic properties, thermal decompositions,
crystal structures, and carbonic anhydrase activities
SEMA CAGLAR*†, ISMIHAN E. AYDEMIR†, MURAT CANKAYA‡,
MEHMET KUZUCU‡, ERSIN TEMEL§ and ORHAN BUYUKGUNGOR§
†Faculty of Arts and Sciences, Department of Chemistry, Erzincan University, Erzincan, Turkey
‡Faculty of Arts and Sciences, Department of Biology, Erzincan University, Erzincan, Turkey
§Faculty of Arts and Sciences, Department of Physics, Ondokuz Mayis University, Samsun, Turkey
(Received 21 October 2013; accepted 18 February 2014)
Cobalt(II) and nickel(II) complexes with diclofenac (dicl) in the presence of nitrogen-donor
3-picoline (3-pic) and 1-(2-aminoethyl)pyrrolidine (2-aepyr), [Co(dicl)2(3-pic)2] (1), [Ni(dicl)2
(3-pic)2(H2O)2] (2), [Co(dicl)2(2-aepyr)2] (3), and [Ni(dicl)2(2-aepyr)2] (4), have been synthesized
and characterized by FT-IR, UV–Vis, elemental and thermal analysis. The crystal structures of 1 and
3 have been determined by single-crystal X-ray diffraction; phase purity of complexes has been
proved by powder X-ray diffraction analysis. Structural analyses have demonstrated that 1 and 3 are
mononuclear and Co(II) ions have distorted octahedral environments. In 1, dicl is bidentate, whereas
in 2, 3, and 4 dicl is monodentate. Dicl ligands are coordinated to metal(II) ions with O of carboxyl-
ate. Therefore, IR spectra of all complexes display {ν(OCO)asym and ν(OCO)sym} of dicl. The calcu-
lated Δν(OCO) values are consistent with the presence of monodentate (>200) and bidentate (<200)
carboxylate. Compounds 2, 3, and 4 exhibit inhibition effects on human carbonic anhydrase-I.
Compounds 3 and 4 show high thermal stability compared with 1 and 2.
Keywords: Diclofenac; Carbonic anhydrase; Nonsteroidal anti-inflammatory drugs; Crystal structure
1. Introduction
Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used as analgesic,
anti-inflammatory, antipyretic agents and are among the most used medical drugs [1].
NSAIDs consist of salicylate derivatives, phenylalkanoic acids, oxicams, anthranilic acids,
*Corresponding author. Email: scaglar@erzincan.edu.tr
© 2014 Taylor & Francis

970
S. Caglar et al.
sulfonamides, and furanones [2]. Diclofenac (dicl), alternatively named 2-(2,6-dicholoroani-
lino)phenylacetic acid, is a part of the NSAIDs group of phenylalkanoic acids. Dicl, in the
form of its water soluble sodium salt, is widely used as analgesic, anti-inflammatory, and
antipyretic agents [3–9]. It is used in sport injuries, painful, and inflammation conditions.
These drugs exhibit an inhibition or activation effect on organism or cells. These effects are
very important to continuation of organism’s life. Organisms contain many vital enzymes
consisting of single or family. Carbonic anhydrase (CA) family controls a crucial biological
function. This family catalyzes the conversion of CO2 and H2CO3 in cells and intercellular
fluid. The reaction of CA catalyzes is essential to physiological processes such as calcifica-
tion, photosynthesis, respiration, ionic, acid–base, and fluid balance, metabolism, and cell
growth [10, 11]. CA-I is the cytosolic form of CA isoforms, present in erythrocytes [12, 13].
Therefore, investigations of inhibition effects of drugs on this CA isoform are crucial for life.
Many spectroscopic and non-spectroscopic techniques were used to explain the sodium
diclofenac (Nadicl) structure. The techniques are as follows: FT-IR [14, 15], calorimetry
[16–18], UV–Vis spectroscopy [19], gas [20, 21] and liquid chromatography [22, 23] and
NMR spectroscopy [24]. The crystal structures of nickel(II), copper(II), cadmium(II), and
tin(IV) complexes with dicl ligands have been determined [4, 14, 25–28]. Compared with
Cu(II) analogs, nickel(II)-dicl complex displayed more biological activity than the parent
drugs [4]. Dicl is a polyfunctional ligand, due to the presence of the negatively charged
carboxylate oxygens.
In the present study, we have focused on the coordination chemistry of dicl with metal
ions in an attempt to examine their mode of binding and inhibitory effects on human blood
carbonic anhydrase I (hCA-I) of the complexes. Here, we report the synthesis, spectral,
thermal characterizations, crystal structures, and inhibitory effects of neutral cobalt(II) and
nickel(II) complexes with dicl in the presence of aromatic 3-picoline (3-pic) and nonaro-
matic 1-(2-aminoethyl)pyrrolidine (2-aepyr).
2. Experimental setup
2.1. Methods of sample characterization
CoCl2·6H2O (Sigma), Ni(NO3)2·6H2O (Sigma), NiCl2·6H2O (Sigma), sodium diclofenac
(Sigma, 99.00%), 3-picoline (Aldrich, 99.00%), and 1-(2-aminoethyl)pyrrolidine (Aldrich,
98.00%) were used for preparation of the complexes. Infrared spectra of the complexes
were recorded with a Thermo Nicolet 6700 spectrophotometer from 4000 to 450 cm−1 at a
resolution of 4 cm−1 using KBr pellets. UV–Vis spectra were recorded on a PG 80+ from
200 to 1100 nm in methanol. C, H, and N elemental analyses were performed on a LECO
CHNS-932 elemental analyzer. The TG and DTA curves were scanned using a PRIS
Diamond TG/DTG apparatus in air (heating rate: 10 °C min−1, platinum crucibles, mass
~10 mg from 30 to 1000 °C). The powder X-ray diffraction (PXRD) patterns of complexes
were taken at ambient temperatures by the use of a PANalytical Empyrean diffractometer
using Ni filtered CuKα radiation (λ = 1.54050 Å; 45 kV, and 40 mA). The theoretical PXRD
patterns were simulated from single-crystal data using PLATON [29].
2.2. Synthesis of [Co(dicl)2(3-pic)2] (1)
CoCl2·6H2O (0.06 g, 0.3 mM) and Nadicl (sodium diclofenac) (0.18 g, 0.6 mM) were dissolved
in ethanol (40 cm3) with continuous stirring at 50 °C. Then, 3-pic (98 μL, 0.6 mM) was added.

Cobalt(II) and nickel(II) diclofenac complexes
971
The resulting solution was allowed to evaporate slowly at room temperature and X-ray quality
purple crystals appeared after a few days. Yield: 80%; Analytical data for [C40H34N4O4Cl4Co]:
Found: C, 57.50; H, 4.10; N, 6.72%; Calcd: C, 57.62; H, 4.07; N, 6.70%.
2.3. Synthesis of [Ni(dicl)2(3-pic)2(H2O)2] (2)
Ni(NO3)2·6H2O (0.06 g, 0.3 mM) and Nadicl (0.18 g, 0.6 mM) were dissolved in methanol
(40 cm3) with continuous stirring at 50 °C. Then, 3-pic (98 μL, 0.6 mM) was added. The
resulting solution was allowed to evaporate slowly at room temperature and green micro-
crystals appeared after one week. Yield: 75%; Analytical data for [C40H38N4O6Cl4Ni]:
Found: C, 55.12; H, 4.21; N, 6.51%; Calcd: C, 55.08; H, 4.36; N, 6.43%.
2.4. Synthesis of [Co(dicl)2(2-aepyr)2] (3)
CoCl2·6H2O (0.06 g, 0.3 mM) and Nadicl (0.18 g, 0.6 mM) were dissolved in ethanol
(40 cm3) with continuous stirring at 50 °C. Then 2-aepyr (0.07 g, 0.6 mM) was added.
The resulting solution was allowed to evaporate slowly at room temperature and X-ray
quality pink crystals appeared after two weeks. Yield: 65%; Analytical data for
[C40H48N6O4Cl4Co]: Found: C, 55.12; H, 5.48; N, 9.72%; Calcd: C, 54.69; H, 5.46; N,
9.57%.
2.5. Synthesis of [Ni(dicl)2(2-aepyr)2] (4)
Complex 4 was prepared in a similar way to 3 with the use of NiCl2·6H2O. The resulting
solution was allowed to evaporate slowly at room temperature and blue microcrystals
appeared after one month. Yield: 86%; Analytical data for [C40H48N6O4Cl4Ni]: Found:
C, 54.80; H, 5.38; N, 9.61 %; Calcd: C, 54.69; H, 5.46; N, 9.57%.
2.6. X-ray crystallography
The diffraction data were collected on a STOE IPDSII image plate detector using Mo Kα
radiation (α = 0.71073 Å, T = 293 K). A summary of the key crystallographic information is
given in table 1. Data collection: Stoe X-AREA [30]. Cell refinement: Stoe X-AREA [30].
Data reduction: Stoe X-RED [30]. The structure was solved by direct-methods using
SHELXS-97 [31] and anisotropic displacement parameters were applied to non-hydrogen
atoms in a full-matrix least-squares refinement based on F2 using SHELXL-97 [31]. All
hydrogens attached to carbon were positioned geometrically and refined by a riding model
with Uiso 1.2 times that of the attached atom; the remaining hydrogens were located from
the Fourier difference map.
2.7. Purification of CA isoenzymes from human blood by affinity chromatography
The purification of hCA-I isoenzyme from human blood erythrocytes was performed in a
simple single-step method by Sepharose-4B-L tyrosine-sulfanilamide affinity gel chroma-
tography. Erythrocytes were purified from fresh human blood obtained from the Blood Cen-
ter of Erzincan State Hospital. Purification methods of CA-I were carried out as previously
described [32, 33].

972
S. Caglar et al.
Table 1. Crystal data and structure refinement parameters for 1 and 3.
1
3
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
b (Å)
c (Å)
α (°)
β (°)
C40H34N4O4CI4Co
835.44
293
0.71073
Triclinic
P-1
C40H48N6O4CI4Co
877.57
293
0.71073
Monoclinic
P 21/c
11.3968 (6)
12.0094 (7)
15.3049 (9)
85.341 (5)
69.477 (4)
82.048 (5)
1941.74 (19)
2
12.9980 (3)
14.6148 (4)
22.0893 (5)
90.00
104.946 (2)
90.00
4054.19 (17)
4
0.736
γ (°)
V (Å)3
Z
A coefficient (mm−1
)
0.763
1.429
DCalcd (mg m−3
)
1.438
Crystal size (mm)
Theta range for data collection (°)
Measured reflections
0.46; 0.53; 0.58
1.92; 28.06
19,762
0.11; 0.24; 0.49
1.39; 27.30
49,580
Independent reflections
Absorption correction
8038
8412
Integrationa
Full-matrix least-squares on F2
0.0623
Integrationa
Full-matrix least-squares on F2
0.0841
Refinement method
Final R indices [F2 >2 σ(F2)]
Goodness-of-fit on F2
1.047
−0.445; 1.437
1.041
−0.48; 0.878
Largest diff. peak and hole (e/Å3)
aStoe and Cie (2002) [31].
2.7.1. Hydratase activity assay. CA activity was assayed by following the hydration of
CO2 according to the method described by Ayvaz et al. [34]. CO2-hydratase activity as an
enzyme unit (EU) was calculated by using the equation (to − tc/tc) where to and tc are the
times for pH change of the non-enzymatic and the enzymatic reactions, respectively.
2.7.2. Esterase activity assay. CA-I activity was determined by following the change in
absorbance at 348 nm of 4-nitrophenylacetate (NPA) to 4-nitrophenylate ion over a period of
3 min at 25 °C using a spectrophotometer according to the method described by Verpoorte
et al. [35]. The inhibitory effects of [Co(dicl)2(3-pic)2], [Ni(dicl)2(3-pic)2(H2O)2],
[Co(dicl)2(2-aepyr)2], and [Ni(dicl)2(2-aepyr)2] were examined. All compounds were tested
in triplicate at each concentration used. Different inhibitor concentrations were used.
HCA-I enzyme activities were measured for [Co(dicl)2(3-pic)2] (0.001–1000 mM),
[Ni(dicl)2(3-pic)2(H2O)2] (0.179–0.299 mM), [Co(dicl)2(2-aepyr)2] (0.342–0.456 mM), and
[Ni(dicl)2(2-aepyr)2] (0.171–0.285 mM) at cuvette concentrations. Control cuvette activity in
the absence of inhibitor was taken as 100%. For each inhibitor, activity (%)–[Inhibitor]
graphs were drawn. To determine Ki values, three different inhibitor concentrations were
tested. In these experiments, NPA was used as substrate at five different concentrations
(0.15–0.75 mM), and Lineweaver–Burk curves were drawn [36].
2.7.3. Protein determination. Protein during the purification steps was determined
spectrophotometrically at 595 nm according to the Bradford method [37].

Cobalt(II) and nickel(II) diclofenac complexes
973
Figure 1. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) bands of carbonic anhydrase
(hCA-I) purified from human blood. Column a: standard proteins, 1: MBP–paramyosin (fusion of MBP and
paramyosin, 80 kDa); 2: MBP–chitin binding domain (CBD) (fusion of MBP and CBD, 58 kDa); 3: soybean
trypsin inhibitor, 24 kDa). Column b: purified hCA-I.

974
S. Caglar et al.
2.7.4. SDS polyacrylamide gel electrophoresis. SDS polyacrylamide gel electrophoresis
was performed after purification of the cord blood isoenzymes. It was carried out according
to the Laemmli procedure [38]. The electrophoretic pattern was photographed (figure 1).
3. Results and discussion
The four diclofenac complexes were synthesized and characterized using FT-IR, UV–Vis,
and elemental and thermal analysis techniques. The crystal structures of [Co(dicl)2(3-pic)2]
and [Co(dicl)2(2-aepyr)2] were determined via single-crystal X-ray diffraction. Selected geo-
metrical parameters for 1 and 3 are listed in table 1. The phase purity of complexes was
confirmed by elemental analysis data and PXRD analysis. Based on the experimental data,
[Ni(dicl)2(2-aepyr)2] is expected to be structurally similar to [Co(dicl)2(2-aepyr)2]. Thermal
analysis and FT-IR spectroscopic techniques show that 2 includes two water ligands,
[Ni(dicl)2(3-pic)2(H2O)2], different from [Co(dicl)2(3-pic)2].
3.1. Description of the crystal structure
3.1.1. [Co(dicl)2(3-pic)2] (1). An ORTEP view of 1 with the atom numbering scheme is
presented in figure 2. Selected bond distances and angles are given in table 2. Single-crystal
X-ray analysis reveals that [Co(dicl)2(3-pic)2] is neutral and crystallizes in the triclinic space
group P-1. Co(II) is coordinated by 3-pic as a monodentate donor via nitrogen and four car-
boxyl oxygens from two dicl ligands in octahedral geometry. Dicl is a bidentate ligand. The
bond angles around cobalt(II) indicate a distortion from ideal octahedral geometry, espe-
cially observed in the bite angles O2–Co1–N1 with the values of 98.24(11)°, O1–Co1–O2
with values of 61.02(7)°, O3–Co1–O4, and O2–Co1–O4 with the values of 61.02(7)° and
108.03(8)°, respectively.
Co–N3-pic bond distances are 2.106(3)–2.131(3) Å, similar with corresponding values in
[Co(bba)2(H2O)2(3-pic)2] (2.15(5) Å) [39], [Co{S2P(OC6H4Me-p)2}2(NC5H4Me-3)2]
(2.1755(3) Å) [40], [Co{S2P(OC6H4Me-p)2}2(C5H5N)2] (2.162(2) Å) [41], and [Co{S2P
(OEt)2}2(C5H5N)2] (2.164(3) Å) [42], where bba, S2P(OC6H4Me-p)2, and NC5H4Me-3 are
2-benzoylbenzoate, bis(O,Oo-ditolyl/dibenzyl/diphenyldithiophosphato), and 3-picoline.
Co-N3-pic bond distances are slightly longer than the 2.046(2) Å found in [Co(3-pic)2Cl2]
[43].
In the present structure, intramolecular N3–H3A···O2 and N4–H4A···O4 hydrogen
bonds generates S(7) ring motives [44]. In addition to those, while intermolecular
C33–H33B···Cl1i (i: 1 − x, 1 − y, 1 − z) hydrogen bonds generate R2 (28) ring motives, the
2
combination of the C33-H33B···Cl1i and C38–H38···O1ii (ii: x, −1 + y, z) hydrogen bonds
4
generate R4 (38) ring motives. These adjacent motives are parallel to the b-axis (figure 3).
The packing pattern generated by hydrogen bonds can be expressed as G(n) form using
graph set notation. G is denoted by S (self) character for the ring generated by intramolecu-
lar hydrogen bonds while if the ring is formed by intermolecular hydrogen bonds, G is
expressed by R (ring) letter. The terms a, d, and n refer to the number of acceptors (a),
donors (d), and atom numbers in the motif.
3.1.2. [Co(dicl)2(2-aepyr)2] (3). The ORTEP view of the asymmetric unit of 3, along with
the atomic numbering scheme, is shown in figure 4. Selected bond lengths and angles of

Cobalt(II) and nickel(II) diclofenac complexes
975
Figure 2. ORTEP III diagram and atom numbering scheme of 1. Displacement ellipsoids are drawn at the 20%
probability level.
Table 2. Selected bond distances (Å) and angles (°) for 1 and 3.
1
Co1–O1
Co1–O2
Co1–O3
2.1217 (19)
2.152 (2)
2.080 (2)
103.34 (8)
96.42 (12)
155.88 (12)
95.75 (9)
98.24 (11)
93.45 (9)
Co1–O4
Co1–N1
Co1–N2
N2–Co1–O2
O1–Co1–O2
N1–Co1–O2
O3–Co1–O4
N2–Co1–O4
O1–Co1–O4
N1–Co1–O4
2.228 (2)
2.131 (2)
2.106 (3)
97.00 (12)
61.02 (7)
94.03 (9)
60.52 (7)
88.48 (10)
89.32 (7)
156.03 (9)
O3–Co1–O1
O3–Co1–N2
N2–Co1–O1
O3–Co1–N1
N2–Co1–N1
O1–Co1–N1
O3–Co1–O2
O2–Co1–O4
162.07 (9)
108.03 (8)
3
Co1–O1
2.095 (2)
Co1–N2
2.349 (3)
Co1–O3
2.077 (2)
Co1–N3
2.111 (3)
Co1–N1
2.116 (3)
Co1–N4
2.322 (3)
O3–Co1–O1
O3–Co1–N3
O1–Co1–N3
O3–Co1–N1
O1–Co1–N1
N3–Co1–N1
O3–Co1–N4
O1–Co1–N4
178.34 (10)
92.60 (11)
88.35 (11)
84.39 (11)
94.71 (11)
176.48 (12)
92.02 (11)
89.47 (11)
N3–Co1–N4
N1–Co1–N4
O3–Co1–N2
O1–Co1–N2
N3–Co1–N2
N1–Co1–N2
N4–Co1–N2
81.05 (11)
97.22 (11)
89.97 (11)
88.50 (11)
102.29 (12)
79.57 (12)
176.04 (11)
the Co(II) complex are given in table 2. Complex 3 crystallizes in the monoclinic space
group P 21/c. Cobalt(II) exhibits a slightly distorted octahedral coordination geometry of
four nitrogens from two 2-aepyr and two dicl ligands. The extent of deviation from an
octahedral geometry varies from 0.3° to 8.95° from the ideal value of 90°.

976
S. Caglar et al.
Figure 3. The molecular packing of 1 showing the formation of R22(28) and R44(38) ring motives. The methyl
pyridine moieties have been omitted for clarity. Symmetry codes: (i) 1 − x, 1 − y, 1 − z; (ii) x, −1 + y, z.
Figure 4. ORTEP III diagram and atom numbering scheme of 3. Displacement ellipsoids are drawn at the 20%
probability level.
The ethyl group (C7–C8 atoms) of 2-aepyr shows disorder. The hydrogen bonding geom-
etries are given in table 3.
Intramolecular N–H···O hydrogen bonds between N–H group of 2-aepyr and carboxyl
oxygen of dicl and also between the N–H group of dicl and carboxyl oxygen of dicl occur.

Cobalt(II) and nickel(II) diclofenac complexes
977
Table 3. Hydrogen-bonding geometries for 1 and 3 (Å, °).
D–H···A
D–H
H···A
D···A
D–H···A
1
N3–H3A···O2
N4–H4A···O4
C33–H33B···Cl1i
C38–H38···O1ii
C24–H24···O1iii
0.86
0.86
0.97
0.93
0.93
2.31
2.27
2.75
2.59
2.56
2.987(3)
2.879(3)
3.710(3)
3.495(5)
3.290(6)
135.5
127.8
173
163
135
3
N1–H1C···O2
N3–H3D···O4
N5–H5···O2
N6–H6···O4
N1–H1D···Cl4i
N3–H3C···Cl3ii
0.90
0.90
0.86
0.86
0.90
0.90
2.07
2.23
2.11
2.27
2.93
2.89
2.830(4)
2.916(4)
2.825(4)
2.937(4)
3.767(3)
3.639(3)
141.3
133.1
139.6
134
155.3
141.3
1 i: 1 − x, 1 − y, 1 − z; ii: −1 + x, y, z; iii: x, −1 + y, z; 3 i: −x + 2, y − 1/2, −z + 3/2; ii: −x + 2, y + 1/2,
−z + 3/2.
Intramolecular N1–H1C···O2 and N3–H3D···O4 hydrogen bonds generate S(6) ring motives
while N5–H5···O2 and N6–H6···O4 hydrogen bonds generate S(7) ring motives [44].
Adjacent complex units are connected via intermolecular N–H···Cl hydrogen bond between
the N–H group of 2-aepyr ligand and chloro atom of dicl ligand. Intermolecular
N1–H1D···Cl4i (i: −x + 2, y − 1/2, −z + 3/2) and N3–H3C···Cl3ii (ii: −x + 2, y + 1/2, −z + 3/2)
2
hydrogen bonds generate adjacent R2 (24) ring motives (figure 5).
Figure 5. The molecular packing of 3 showing formation of R22(24) ring motives. The pyrrolidine moieties have
been omitted for clarity. Symmetry codes: (i) −x + 2, y − 1/2, −z + 3/2; (ii) −x + 2, y + 1/2, −z + 3/2.

978
S. Caglar et al.
3.2. Powder X-ray diffraction
PXRD was performed on the metal complexes (figure 6). The PXRD patterns of the com-
plexes demonstrated sharp intense peaks indicating their crystalline phase. The experimental
PXRD patterns of 1 and 3 closely match simulations obtained from the appropriate single
XRD measurements, confirming phase purity of the products [45]. However, some small
differences were observed in the intensities of reflections. The differences in intensity may
be due to preferred orientation of crystallites in powder samples [45]. Comparison of simu-
lated and experimental PXRD patterns of 1 and 3 is given in figures 7 and 8, respectively.
3.3. IR spectra
The band assignments of Nadicl and complexes are listed in table 4. ν(NH) of a secondary
amino group of Nadicl is observed at 3250 cm−1. In complexes, this band is at 3236, 3232,
3198, and 3201 cm−1, respectively. The band at 3347 cm−1 for 3 and 3353 cm−1 for 4 could
be ascribed to stretch of N–H, suggesting the presence of amino group of 1-(2-aminoethyl)
pyrrolidine. A broad functional group region indicates that water participated in the coordi-
nation in 2. The band at 3304 cm−1 corresponds to the O–H stretch of water. The asymmet-
ric and symmetric stretching peaks of both aromatic and aliphatic ν(CH) bonds of Nadicl,
3-picoline and 1-(2-aminoethyl)pyrrolidine are at 3063–2832 cm−1. The νasym(COO–) of free
Nadicl at 1572 cm−1 shifts to 1548, 1579, 1577, and 1577 cm−1 for complexes, νsym(COO–)
at 1399 cm−1 shifts in complexes to 1418, 1379, 1368, and 1368 cm−1, respectively. The dif-
ference Δν [νasym(COO) – νsym(COO)], a useful tool for determining the coordination mode
of carboxylate ligands, is calculated as 130, 200, 209, and 209 cm−1, respectively, bidentate
Figure 6. PXRD patterns for (a) 1, (b) 2, (c) 3, and (d) 4.

Cobalt(II) and nickel(II) diclofenac complexes
979
Figure 7. Experimental (a) and simulated (b) PXRD patterns for 1.
(<200 cm−1) coordination for 1; monodentate (>200 cm−1) coordination for 2, 3, and 4 [46].
Bands at 1613–1604 cm−1 arise from phenyl ring stretching vibrations of Nadicl and other
ligands. Medium intensity bands at 1312–1309 cm−1 may be assigned to ν(C–N–C)
asymmetric stretch while weak bands at 1239 cm−1 are assigned to ν(C–N–C) symmetric
stretch of Nadicl. The band attributed to in plane deformation vibration of the ν(CH) occurs
at 940 cm−1. Bands at 760 cm−1 correspond to ν(C–Cl) of Nadicl. The band under
600 cm−1 in complexes may be attributed to metal–oxygen and metal–nitrogen stretches.
3.4. UV–Vis spectra
The electronic absorption spectra of 1–4 were recorded at room temperature in methanol.
Each complex shows an absorption lower than 370 nm due to intramolecular π→π* and
n→π* transitions for the aromatic ring. The absorption spectrum of 1 has three bands, the
4
band at 980 nm may be attributed to a T1g(F)→4T2g(F) transition, a band exists at 468 nm
4
(ε = 18 dm3 M−1 cm−1) due to d–d transition from a T1g(F)→4A2g(F), and the third band at
4
390 nm may be attributed to a T1g(F) →4T1g(P) transition. Complex 3 in the visible
region has two low intensity bands assigned to d–d transitions. These bands at 540 nm

980
S. Caglar et al.
Figure 8. Experimental (a) and simulated (b) PXRD patterns for 3.
Table 4. Selected IR spectral dataa for dicl, 1, 2, 3, and 4.
dicl
1
2
3
4
ν(NH)dicl
ν(NH)2-aepyr
ν(OH)
3250m
–
–
3060w
2980w
1572s
1399w
1306s
1236vw
768 mw
3236m
–
–
3010w
2854w
1548s
1418w
1305s
1237w
758mw
3232m
–
3198m
3347m
–
3015w
2974–2832m
1577s
3201m
3353m
–
3045w
2974–2838m
1577s
3304b,m
3063w
2813w
1577s
1385w
1312s
1239w
758m
ν
ν
ν
ν
ν
ν
aro(CH)
alf(CH)
asym(COO–)
sym(COO–)
asym(CNC)
sym(CNC)
1368w
1309s
1241w
760w
1368w
1309s
1241w
760w
ν(CCl)
Note: w, weak; m, medium; s, strong; vs, very strong; b, broad.
aFrequencies in cm−1
.

Cobalt(II) and nickel(II) diclofenac complexes
981
(ε = 5 dm3 M−1 cm−1) and 693 nm (ε = 15 dm3 M−1 cm−1) may be attributed to
4
4T1g(F)→4A2g(F) and T1g(F)→4T2g(F) transitions, respectively, and a third band
(4T1g(F)→4T1g(P) transition) is observed at 388 nm. The absorption spectra of 2 and 4
(Ni2+ complexes) showed three bands at 980 and 970 nm, 478 nm (ε = 9 dm3 M−1 cm−1) and
550 (ε = 12 dm3 M−1 cm−1), 391 and 390 nm assigned to the spin allowed transitions
3
3
3A2g(F)→3T2g(F), A2g(F)→3T2g(F) and A2g(F)→3T1g(P), respectively (figure 9).
3.5. Thermal analysis
Complex 1 begins to decompose at 152 °C, from elimination of 0.5 M 3-pic with the endo-
thermic step in DTA at 156 °C (DTGmax. 113 and 224 °C). The experimental mass loss of
5.70% agrees with the calculated mass loss of 5.58%. In the second step, from 175 to
673 °C, the degradation of 1.5 M 3-pic and two dicl occurs with a mass loss of 85.30%
(Calcd 87.61%; DTGmax. 502 °C). The second step with one sharp and a medium exother-
mic DTA peaks at 257 and 503 °C results in formation of CoO [figure 10(a)].
The thermal decomposition of 2 occurs in three steps. The first step from 30 to 103 °C is
assigned to loss of two waters with weight loss of 5.10% (calculated 4.12%, endothermic
DTA peak at 95 °C). The second step from 103 to 257 °C corresponds to loss of two 3-pic,
with the endothermic steps in the DTA at 118 and 221 °C. The experimental mass loss of
20.84% agrees with the calculated mass loss of 21.24% (DTGmax. 113 and 224 °C). The
third step from 242 to 597 °C corresponds to exothermic removal of two dicl with the exo-
thermic DTA maxima at 480 and 535 °C. Good agreement between the experimental and
calculated values was observed for the mass loss (exp. 68.50%; Calcd 67.96%; DTGmax.
267 and 534 °C). The final thermal product is NiO, obtained at 597 °C [figure 10(b)].
Figure 9. UV–Vis spectra of (a) 1, (b) 2, (c) 3, and (d) 4.

982
S. Caglar et al.
Figure 10. TG–DTA–DTG curves of (a) 1, (b) 2, (c) 3, and (d) 4.
The TG curve of 3 is shown in figure 10(c). The first endothermic stage (DTA at 183 °C)
is related to removal of one 2-aepyr from 30 to 215 °C (DTGmax. 180 °C, mass loss
13.50%, Calcd 13.01%). The second stage between 215 and 524 °C is related to release of
one 2-aepyr and one dicl (DTA at 500 °C; DTGmax. 252 and 502 °C; exp. 46.05; Calcd
46.74%). The third stage (DTA at 548 °C; DTGmax 548 °C) between 524 and 598 corre-
sponds to loss of the remaining dicl (exp. 32.45%; calc. 33.74%). The final decomposition
product is CoO.
The thermal behavior of 4 was followed to 900 °C in a static atmosphere of air. Complex
4 decomposes in three stages with the first stage at 30–248 °C corresponding to removal of
one 2-aepyr with endothermic steps in the DTA at 208 °C (exp. mass loss 12.70%; Calcd
13.01%; DTGmax. 207 and 218 °C). The second stage between 248 and 290 °C corresponds
to loss of the remaining 2-aepyr (DTA at 283 °C; DTGmax. 267 °C; exp. mass loss 13.05%;
Calcd 13.01%). The following stage from 290 to 603 °C is related to release of two dicl
ligands with DTA maxima at 301 and 534 °C (DTGmax. 303 and 532 °C; exp. mass loss
66.35%; Calcd 67.48%). The final decomposition product is NiO [figure 10(d)].
3.6. Purification and enzymatic activity of CA-I
Purifications of CAs have been made so many times for the different organisms, and the
effects of various chemicals were checked on these isoforms [10, 32–34]. CA-I was purified
from human blood erythrocytes by affinity chromatography. The purified enzyme was char-
acterized with a specific activity of 1210.46 EU/mg proteins, a yield of 60.00%, and a puri-
fication coefficient of 127.69 (table 5). The inhibitory effects of the neutral cobalt(II) and

Cobalt(II) and nickel(II) diclofenac complexes
983
Table 5. Inhibitory activities of synthesized complexes.
I50
Ki
Complexes
CA-I (mM)
CA-I (mM)
Inhibition type
Ni(dicl)2(3-pic)2(H2O)2]
[Ni(dicl)2(2-aepyr)2]
[Co(dicl)2(2-aepyr)2]
0.223
0.231
0.391
0.188
0.173
0.340
Non-competitive
Non-competitive
Non-competitive
Table 6. Purification of hCA-I.
Total
volume
(mL)
Total
protein
(mg)
Total
activity
(EU)
Specific
activity
(EU/mg)
Activity
Protein
(mg/mL)
Recovery Purification
Step
(EU/mL)
(%)
(Fold)
Hemolysate
hCA-I
171.00
462.00
39.00
8.65
18.03
0.38
703.17
3.29
6669.00
3982.44
9.48
1210.46
100
60
1.00
127.69
*Mean value from at least three different measurements. Errors were in the range of 3–5% of the obtained value (data not
shown).
nickel(II) complexes with diclofenac in the presence of aromatic 3-picoline (3-pic) and non-
aromatic 1-(2-aminoethyl)pyrrolidine (2-aepyr) were tested in vitro. The inhibitor concentra-
tions that caused 50% inhibition (IC50) were determined from % activity versus [Inhibitor]
plots, and the Ki values were calculated from Lineweaver–Burk plots (table 6).
3.6.1. Investigation of inhibition type of CA. We prepared four chemical structures
shown in figure 1 and evaluated their ability to inhibit hCA-I over a wide range of concen-
trations (0.001–1000 mM). Three of the four compounds inhibited hCA-I (table 6). Investi-
gations show that many different chemicals and drugs inhibited hCA-I [32–34].
[Ni(dicl)2(3-pic)2(H2O)2], [Co(dicl)2(2-aepyr)2], and [Ni(dicl)2(2-aepyr)2] at low concentra-
tions showed in vitro inhibitory effects on hCA-I. [Ni(dicl)2(2-aepyr)2] had the strongest
inhibitory effects on hCA-I.
4. Conclusion
We have synthesized four new diclofenac cobalt(II) and nickel(II) complexes and studied
their structural properties using FT-IR and UV–Vis spectroscopies, thermal analysis, and
X-ray diffraction techniques. X-ray crystal structure analysis demonstrated that 1 and 3 have
distorted octahedral geometry. Intramolecular N3–H3A···O2 and N4–H4A···O4 hydrogen
bonds generate S(7) ring motives for 1. Intramolecular N1–H1C···O2 and N3–H3D···O4
hydrogen bonds generate S(6) ring motives while N5–H5···O2 and N6–H6···O4 hydrogen
bonds generate S(7) ring motives for 3. Intra- and intermolecular hydrogen bonds stabilize
this arrangement. 3 and 4 demonstrate higher thermal stability than 1 and 2. Δν indicates
bidentate (<200 cm−1) coordination for 1; monodentate (>200 cm−1) for 2, 3, and 4. These
compounds were checked for inhibition effects on hCA-I with 2, 3, and 4 showing
non-competitive inhibition.

984
S. Caglar et al.
Supplementary material
Supplementary data CCDC-932105 and CCDC-932104 contain the supplementary
crystallographic data for 1 and 3, respectively. These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crys-
tallographic Data Center, 12 Union Road, Cambridge CB2 1EZ, UK; Fax: (+44) 1223
336 033; or E-mail: deposit@ccdc.cam.ac.uk.
Funding
This work was financially supported by the Erzincan University under the project no. 110205.
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